Rotogravure cylinders (see FIG. 1 which shows such a cylinder, and FIG. 2 which shows a typical cross section of such a cylinder) comprise of the base 1, which is usually made of steel or aluminium with a diameter as required by the printing machine, an image carrying copper layer 2 usually of 0.1 to 1 mm thick where the packaging pattern is engraved upon, and a chrome layer 3 usually 6 to 8 μm thick to increase resistance of the cylinder to wear during the printing process. In FIG. 1 the dimensions shown are not in scale and are shown for descriptive purposes.
A rotogravure life cycle starts with the copper plating, engraving with the required packaging pattern and chrome plating of the cylinder before it is used in the printing machine. The cylinder life cycle continuous at the printing machine with the printing of packaging material. Finally, the cylinder life cycle ends when the industry using the particular cyclinder decides to modify of change the packaging pattern.
US 2011/0083570 describes a process for refurbishing cylinder rollers for use in printing machines wherein an intermediate polymer material layer is placed between the core surface and the image carrying layer of the cylinder, having a conductivity to permit electroplating. The disadvantage of the disclosed process is that an intermediate polymer layer is used for the construction of a refurbished rotogravure cylinder. The disclosed intermediate polymer layer is a soft material which leads to a limited life time in printing processes due to the constantly applied forces onto the rotogravure cylinder. Further, the process is problematic with regard to the diameter stability. More specifically, shrink tape is necessary to ensure an intermediate polymer layer having a stable diameter.
Accordingly, there is a need in the art for a simple and effective process for the refurbishment of user rotogravure cylinders, which provides rotogravure cylinders having a stable diameter and high wear resistance.
A further problem in relation to the prior art method is that the refurbishment does not result in cylinder having use-properties that are substantially the same as those of new cylinders. Particularly, cylinders are engraved with a engraving pattern and are thereafter used in printing processes with predefined use settings, such as at a predefined rotation speed, with a certain amount and type of ink and at a specific pressure. Preferably, the use settings are the same for all cylinders, or at least for a plurality of cylinders. Hence, the use-properties of refurbished cylinders, such as the hardness, are preferably at least substantially the same as those of new cylinders, so that the use settings can remain the same, and the risk of malfunctioning in printing due to variation of use-settings is minimized.